<script id="draw-shader-vs" type="x-shader/x-vertex">
precision mediump float;

attribute vec3 inPos;
attribute vec3 inNV;
attribute vec3 inCol;

varying vec3 vertPos;
varying vec3 vertNV;
varying vec3 vertCol;
varying vec4 vPosPrj;

uniform mat4 u_projectionMat44;
uniform mat4 u_modelViewMat44;

void main()
{
    vertNV      = mat3( u_modelViewMat44 ) * normalize( inNV );
    vertCol     = inCol;
    vec4 pos    = u_modelViewMat44 * vec4( inPos, 1.0 );
    vertPos     = pos.xyz / pos.w;
    vPosPrj     = u_projectionMat44 * pos;
    gl_Position = vPosPrj;
}
</script>

<script id="draw-shader-fs" type="x-shader/x-fragment">
precision mediump float;

varying vec3 vertPos;
varying vec3 vertNV;
varying vec3 vertCol;
varying vec4 vPosPrj;

uniform vec2 u_depthRange;

vec3 PackDepth( in float depth )
{
    float depthVal = depth * (256.0*256.0*256.0 - 1.0) / (256.0*256.0*256.0);
    vec4 encode = fract( depthVal * vec4(1.0, 256.0, 256.0*256.0, 256.0*256.0*256.0) );
    return encode.xyz - encode.yzw / 256.0 + 1.0/512.0;
}

void main()
{
    float ndc_depth = vPosPrj.z / vPosPrj.w;
    float nearZ     = u_depthRange.x;
    float farZ      = u_depthRange.y;
    //float depth     = (((farZ-nearZ) * ndc_depth) + nearZ + farZ) / 2.0;
    float depth     = ndc_depth * 0.5 + 0.5;
    gl_FragColor    = vec4( PackDepth( depth ).xyz, 1.0 );
} 
</script>

<script id="ssao-shader-vs" type="x-shader/x-vertex">
    precision mediump float;
    
    attribute vec2 inPos;
    varying   vec2 vPos;
    varying   vec3 vCornerPos;

    uniform vec2  u_depthRange;
    uniform float u_tanFOV_2;
    uniform vec2  u_viewportsize;
    
    void main()
    {
        float aspect = u_viewportsize.x / u_viewportsize.y;
        float farLen = u_tanFOV_2 * u_depthRange.y;
        vPos         = inPos;
        vCornerPos   = vec3( inPos.x * aspect * farLen, inPos.y * farLen, -u_depthRange.y );
        gl_Position  = vec4( inPos, 0.0, 1.0 );
    }
</script>

<script id="ssao-shader-fs" type="x-shader/x-fragment">
    precision mediump float;
    
    varying vec2 vPos;
    varying vec3 vCornerPos;
    
    uniform sampler2D u_depthSampler;
    uniform sampler2D u_ssaoKernelSampler;
    uniform sampler2D u_ssaoNoiseSampler;
    uniform float     u_radius;
    uniform vec2      u_viewportsize;
    uniform vec2      u_depthRange;
    uniform float     u_tanFOV_2;
    uniform mat4      u_projectionMat44;
    
    float UnpackDepth( in vec3 pack )
    {
      float depth = dot( pack, 1.0 / vec3(1.0, 256.0, 256.0*256.0) );
      return depth * (256.0*256.0*256.0) / (256.0*256.0*256.0 - 1.0);
    }
  
    float Depth( in sampler2D depthSampler, in vec2 texC )
    {
      vec3 depthVal = texture2D( depthSampler, texC.st ).xyz;  
      return UnpackDepth( depthVal.rgb );
    }

    vec3 GetNormalFromDepthValue( float depth, vec2 vUV )
    {    
        vec2 offsetX = vec2(1.0/u_viewportsize.x, 0.0);
        vec2 offsetY = vec2(0.0, 1.0/u_viewportsize.y);
    
        float depthOffsetX = Depth(u_depthSampler, vUV + offsetX); // Horizontal neighbour
        float depthOffsetY = Depth(u_depthSampler, vUV + offsetY); // Vertical neighbour
        vec3 normal = vec3(0.0);
    
        vec3 pX = vec3(offsetX, depthOffsetX - depth);
        vec3 pY = vec3(offsetY, depthOffsetY - depth);
        normal = cross(pY, pX);
        normal.z = abs(normal.z); // We want normal.z positive
    
        return normalize(normal); // [-1,1]
    }

    float DepthToZ( in float depth )
    {
        float near  = u_depthRange.x; // distance to near plane (absolute value)
        float far   = u_depthRange.y; // distance to far plane (absolute value)
        float z_ndc = 2.0 * depth - 1.0;
        float z_eye = 2.0 * near * far / (far + near - z_ndc * (far - near));
        return -z_eye;
    }
    
    void main()
    {
        float depthBias = 1.0e-5;
        float power = 1.0;

        float aspect    = u_viewportsize.x / u_viewportsize.y;
        vec2  texC      = vPos.st * 0.5 + 0.5;
        vec4  texCol    = texture2D( u_depthSampler, texC );
        float fragDepth = Depth( u_depthSampler, texC );
        float far       = u_depthRange.y;
        vec3  fragNV    = GetNormalFromDepthValue( fragDepth, texC );

        float ambientOcclusion = 1.0;
        float alpha = 0.0;
        if (fragDepth > 0.0)
        {
            vec2 noiseScale   = u_viewportsize.xy / 4.0;
            vec4 randomVal    = texture2D( u_ssaoNoiseSampler, texC.st * noiseScale );
            vec3 randomVec    = randomVal.xyz * 2.0 - 1.0;
            vec3 tangent      = normalize( randomVec - fragNV * dot( randomVec, fragNV ) );
            mat3 TBN          = mat3( tangent, cross( fragNV, tangent ), fragNV );

            //vec3 fragPosition = vCornerPos * abs( DepthToZ(fragDepth) / far );
            //vec3 fragPosition = vec3( vPos.xy * u_tanFOV_2 * vec2(aspect, 1.0 ), -1.0 ) * abs(DepthToZ(fragDepth));
            vec3 fragPosition = vec3( vPos.x / u_projectionMat44[0][0], vPos.y / u_projectionMat44[1][1], -1.0 ) * abs(DepthToZ(fragDepth));
        
            float occlusion = 0.0;
            for (int inx = 0; inx < 32; inx++)
            {
                //vec3 samplePosition = fragPosition + u_radius * TBN * kernelSamples[i];
                vec4 sampleVal = texture2D( u_ssaoKernelSampler, vec2( float( inx ) / 32.0, 0.0 ) );
                vec3 samplePosition = fragPosition + u_radius * TBN * sampleVal.xyz;
        
                // Project sample position from view space to screen space:
                vec4 offset = u_projectionMat44 * vec4(samplePosition, 1.0);
                offset.xy /= offset.w; // Perspective division -> [-1,1]
                offset.xy = offset.xy * 0.5 + 0.5; // [-1,1] -> [0,1]
        
                // Get current sample depth:
                float sampleZ = DepthToZ( Depth(u_depthSampler, offset.xy) );
        
                // Range check and accumulate if fragment contributes to occlusion:
                float rangeCheck = step( abs(fragPosition.z - sampleZ), u_radius );
                occlusion += step( samplePosition.z - sampleZ, -depthBias ) * rangeCheck;
            }
            // Inversion
            ambientOcclusion = 1.0 - (occlusion / 32.0);
            ambientOcclusion = pow(ambientOcclusion, power);
            alpha = 1.0;
        }
        gl_FragColor = vec4(vec3(ambientOcclusion), alpha);
        
        //gl_FragColor = vec4( vec3( 1.0 - fragDepth ), 1.0 );
        //gl_FragColor = vec4( fragNV * 0.5 + 0.5, 1.0 );
        //gl_FragColor = vec4( abs( fragNV ), 1.0 );
    }
</script>

<script id="blur-shader-vs" type="x-shader/x-vertex">
    precision mediump float;
    
    attribute vec2 inPos;
    
    varying   vec2 pos;
    
    void main()
    {
        pos = inPos;
        gl_Position = vec4( inPos, 0.0, 1.0 );
    }
</script>

<script id="blur-shader-fs" type="x-shader/x-fragment">
precision mediump float;

varying vec2 pos;

uniform sampler2D u_ssaoSampler;
uniform vec2      u_viewportsize;
uniform float     u_blur;

float SSAO44( in sampler2D ssaoSampler, in vec2 texC )
{
    vec2 texOffs = 1.0 / u_viewportsize;
    float ssao = 0.0;  
    for ( int inxX = -1; inxX < 3; ++ inxX )
    {
        for ( int inxY = -1; inxY < 3; ++ inxY )
            ssao += texture2D( ssaoSampler, texC.st + texOffs * vec2( int(inxX), int(inxY) ) ).x;
    }
    return ssao / 16.0;
}

void main()
{
    vec2 texC    = pos.st * 0.5 + 0.5;
    vec4 texCol  = texture2D( u_ssaoSampler, texC );
    float ssao   = SSAO44( u_ssaoSampler, texC );
    ssao         = mix( texCol.r, ssao, u_blur );
    gl_FragColor = vec4( mix( vec3(0.9, 0.7, 0.9), vec3( ssao ), texCol.a ), 1.0 );
    //gl_FragColor = vec4( texCol.xyz, 1.0 );
}
</script>

<style>
html,body { margin: 0; overflow: hidden; }
#gui { position : absolute; top : 0; left : 0; font-size : large; }
#ref-link { position : absolute; bottom : 0; left : 0; font-size : large; }  
</style>

<body>

<div>
<form id="gui" name="inputs">
    <table>
        <tr> <td> <font color=#40f040>radius</font> </td> 
                <td> <input type="range" id="radius" min="0" max="100" value="60"/></td></tr>
        <tr> <td> <font color=#40f040>blur</font> </td> 
                <td> <input type="checkbox" id="blur" value="1" /></td></tr>
    </table>
</form>
</div>

<canvas id="glow-canvas" style="border: none;" width="512" height="512"></canvas>


<a id="ref-link" href="https://stackoverflow.com/questions/46079061/ssao-implementation-in-babylon-js-and-glsl-using-view-ray-for-depth-comparison/46084410#46084410">
SSAO implementation in Babylon JS and GLSL, using view ray for depth comparison 
</a>

</body>

<script type="text/javascript">

(function loadscene() {

var sliderScale = 100.0
var gl;
var canvas;
var bufCube = {};
var bufTorus = {}
var bufSSAOQuad = {};
var bufQuad = {};
var progDraw; 
var progSSAO;
var progBlur;
var ssaoTextures;
var camera;
var vp_size;

function render(deltaMS) {

    var shininess = 10.0;
    var radius = 0.2 + 0.6 * document.getElementById( "radius" ).value / sliderScale;
    var blur = document.getElementById( "blur" ).checked;
    var blurVal = blur ? 1 : 0 
    
    vp_size = [canvas.width, canvas.height];
    camera.Update( vp_size );
        
    gl.enable( gl.DEPTH_TEST );
    gl.clearColor( 0.0, 0.0, 0.0, 1.0 );

    // set up framebuffer
    blurFB[0].Bind( true );
    
    // set up draw shader
    var prjMat = camera.Perspective();
    ShProg.Use( progDraw );
    ShProg.SetM44( progDraw, "u_projectionMat44", prjMat );
    var viewMat = camera.Orbit();
    var modelMat = IdentM44();
    modelMat = camera.AutoModelMatrix();
    //modelMat = RotateAxis( viewMat, -60.0 * Math.PI / 180.0, 0 );
    //modelMat = RotateAxis( viewMat, -30.0 * Math.PI / 180.0, 1 );
    //modelMat = RotateAxis( viewMat, CalcAng( deltaMS, 13.0 ), 0 );
    //modelMat = RotateAxis( viewMat, CalcAng( deltaMS, 17.0 ), 1 );
    ShProg.SetM44( progDraw, "u_modelViewMat44", Multiply(viewMat, modelMat) );
    ShProg.SetF2( progDraw,  "u_depthRange", [ camera.near, camera.far ] );
    
    // draw scene
    for( objI = 0; objI < 2; ++ objI )
        VertexBuffer.Draw( objI == 0 ? bufCube : bufTorus );

    // set blur-X framebuffer and bind framebuffer texture
    blurFB[1].Bind( true );
    var texUnit = 1;
    blurFB[0].BindTexture( texUnit );
   
    // set up SSAO shader
    var tanFOV_2 = Math.tan( Math.PI * camera.fov_y / 360 );
    ShProg.Use( progSSAO );
    ShProg.SetI1( progSSAO, "u_depthSampler", texUnit )
    ShProg.SetI1( progSSAO, "u_ssaoKernelSampler", ssaoTextures.kernelTexUnit )
    ShProg.SetI1( progSSAO, "u_ssaoNoiseSampler", ssaoTextures.noiseTexUnit )
    ShProg.SetF1( progSSAO, "u_radius", radius );
    ShProg.SetF2( progSSAO, "u_viewportsize", [ blurFB[0].width, blurFB[0].height ] );
    ShProg.SetF2( progSSAO, "u_depthRange", [ camera.near, camera.far ] );
    ShProg.SetF1( progSSAO, "u_tanFOV_2", tanFOV_2 );
    ShProg.SetM44( progSSAO, "u_projectionMat44", prjMat );
    
    // draw full screen space
    VertexBuffer.Draw( bufSSAOQuad );

    // reset framebuffer and bind frambuffer texture
    blurFB[1].Release( true );
    gl.viewport( 0, 0, canvas.width, canvas.height );
    texUnit = 2;
    blurFB[1].BindTexture( texUnit );

    // set up blur process shader
    ShProg.Use( progBlur );
    ShProg.SetI1( progBlur, "u_ssaoSampler", texUnit )
    ShProg.SetF2( progBlur, "u_viewportsize", [ blurFB[1].width, blurFB[1].height ] );
    ShProg.SetF1( progBlur, "u_blur", blurVal );
    
    // draw full screen space
    VertexBuffer.Draw( bufQuad );

    requestAnimationFrame(render);
}

function initScene() {

    document.getElementById( "blur" ).checked = true;
    canvas = document.getElementById( "glow-canvas");
    vp_size = [canvas.width, canvas.height];
    gl = canvas.getContext( "experimental-webgl" );
    if ( !gl )
      return;

    progDraw = ShProg.Create( 
      [ { source : "draw-shader-vs", stage : gl.VERTEX_SHADER },
        { source : "draw-shader-fs", stage : gl.FRAGMENT_SHADER }
      ] );
    progDraw.inPos = ShProg.AttrI( progDraw, "inPos" );
    progDraw.inNV  = ShProg.AttrI( progDraw, "inNV" );
    progDraw.inCol = ShProg.AttrI( progDraw, "inCol" );
    if ( progDraw.prgObj == 0 )
        return;

    progSSAO = ShProg.Create( 
      [ { source : "ssao-shader-vs", stage : gl.VERTEX_SHADER },
        { source : "ssao-shader-fs", stage : gl.FRAGMENT_SHADER }
      ] );
    progSSAO.inPos = ShProg.AttrI( progSSAO, "inPos" );
    if ( progSSAO.progObj == 0 )
        return;

    progBlur = ShProg.Create( 
      [ { source : "blur-shader-vs", stage : gl.VERTEX_SHADER },
        { source : "blur-shader-fs", stage : gl.FRAGMENT_SHADER }
      ] );
    progBlur.inPos = ShProg.AttrI( progBlur, "inPos" );
    if ( progBlur.progObj == 0 )
        return; 

    var cubePos = [
        -1.0, -1.0,  1.0,  1.0, -1.0,  1.0,  1.0,  1.0,  1.0, -1.0,  1.0,  1.0,
        -1.0, -1.0, -1.0,  1.0, -1.0, -1.0,  1.0,  1.0, -1.0, -1.0,  1.0, -1.0 ];
    var cubeCol = [ 1.0, 0.0, 0.0, 1.0, 0.5, 0.0, 1.0, 0.0, 1.0, 1.0, 1.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 1.0 ];
    var cubeHlpInx = [ 0, 1, 2, 3, 1, 5, 6, 2, 5, 4, 7, 6, 4, 0, 3, 7, 3, 2, 6, 7, 1, 0, 4, 5 ]; 
    var cubePosData = [];
    var cubeLen = 0.9;
    for ( var i = 0; i < cubeHlpInx.length; ++ i ) {
        cubePosData.push( cubePos[cubeHlpInx[i]*3]*cubeLen, cubePos[cubeHlpInx[i]*3+1]*cubeLen, cubePos[cubeHlpInx[i]*3+2]*cubeLen );
    }
    var cubeNVData = [];
    for ( var i1 = 0; i1 < cubeHlpInx.length; i1 += 4 ) {
        var nv = [0, 0, 0];
        for ( i2 = 0; i2 < 4; ++ i2 ) {
            var i = i1 + i2;
            nv[0] += cubePosData[i*3]; nv[1] += cubePosData[i*3+1]; nv[2] += cubePosData[i*3+2];
        }
        for ( i2 = 0; i2 < 4; ++ i2 )
          cubeNVData.push( nv[0], nv[1], nv[2] );
    }
    var cubeColData = [];
    for ( var is = 0; is < 6; ++ is ) {
        for ( var ip = 0; ip < 4; ++ ip ) {
           cubeColData.push( cubeCol[is*3], cubeCol[is*3+1], cubeCol[is*3+2] ); 
        }
    }
    var inxData = [];
    for ( var i = 0; i < cubeHlpInx.length; i += 4 ) {
        inxData.push( i, i+1, i+2, i, i+2, i+3 );
    }
    bufCube = VertexBuffer.Create(
        [ { data : cubePosData, attrSize : 3, attrLoc : progDraw.inPos },
          { data : cubeNVData,  attrSize : 3, attrLoc : progDraw.inNV },
          { data : cubeColData, attrSize : 3, attrLoc : progDraw.inCol } ],
          inxData
      );

    // create torus
    var circum_size = 32, tube_size = 32;
    var rad_circum = 1.3;
    var rad_tube = 0.4;
    var torus_pts = [];
    var torus_nv = [];
    var torus_col = [];
    var torus_inx = [];
    var col = [1, 0.5, 0.0];
    for ( var i_c = 0; i_c < circum_size; ++ i_c ) {
        var center = [
            Math.cos(2 * Math.PI * i_c / circum_size),
            Math.sin(2 * Math.PI * i_c / circum_size) ]
        for ( var i_t = 0; i_t < tube_size; ++ i_t ) {
            var tubeX = Math.cos(2 * Math.PI * i_t / tube_size)
            var tubeY = Math.sin(2 * Math.PI * i_t / tube_size)
            var pt = [
                center[0] * ( rad_circum + tubeX * rad_tube ),
                center[1] * ( rad_circum + tubeX * rad_tube ),
                tubeY * rad_tube ]
            var nv = [ pt[0] - center[0] * rad_tube, pt[1] - center[1] * rad_tube, tubeY * rad_tube ]
            torus_pts.push( pt[0], pt[1], pt[2] );
            torus_nv.push( nv[0], nv[1], nv[2] );
            torus_col.push( col[0], col[1], col[2] );
            var i_cn = (i_c+1) % circum_size
            var i_tn = (i_t+1) % tube_size
            var i_c0 = i_c * tube_size; 
            var i_c1 = i_cn * tube_size; 
            torus_inx.push( i_c0+i_t, i_c0+i_tn, i_c1+i_t, i_c0+i_tn, i_c1+i_t, i_c1+i_tn )
        }
    }
    bufTorus = VertexBuffer.Create(
        [ { data : torus_pts, attrSize : 3, attrLoc : progDraw.inPos },
          { data : torus_nv,  attrSize : 3, attrLoc : progDraw.inNV },
          { data : torus_col, attrSize : 3, attrLoc : progDraw.inCol } ],
          torus_inx
      );

    bufSSAOQuad = VertexBuffer.Create( 
        [ { data : [ -1.0, -1.0, 1.0, -1.0, 1.0, 1.0, -1.0, 1.0 ], attrSize : 2, attrLoc : progSSAO.inPos } ],
        [ 0, 1, 2, 0, 2, 3 ]
    );

    bufQuad = VertexBuffer.Create( 
        [ { data : [ -1.0, -1.0, 1.0, -1.0, 1.0, 1.0, -1.0, 1.0 ], attrSize : 2, attrLoc : progBlur.inPos } ],
        [ 0, 1, 2, 0, 2, 3 ]
    );

    ssaoTextures = generateSSAOTextures( 32, 4, 3, 4 );   

    camera = new Camera( [0, 2.6, 0.0], [0, 0, 0], [0, 0, 1], 90, vp_size, 0.1, 20 );

    window.onresize = resize;
    resize(); 
    requestAnimationFrame(render);
}

function resize() {
    //vp_size = [gl.drawingBufferWidth, gl.drawingBufferHeight];
    vp_size = [window.innerWidth, window.innerHeight];
    //vp_size = [256, 256]
    canvas.width = vp_size[0];
    canvas.height = vp_size[1];

    var fbsize = Math.max(vp_size[0], vp_size[1]);
    fbsize = 1 << 31 - Math.clz32(fbsize); // nearest power of 2

    var fb_rect = [fbsize, fbsize];
    blurFB = [ FrameBuffer.Create( fb_rect ), FrameBuffer.Create( fb_rect ) ]; 
}


function IdentM44() { return [1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1]; }

function RotateAxis(matA, angRad, axis) {
    var aMap = [ [1, 2], [2, 0], [0, 1] ];
    var a0 = aMap[axis][0], a1 = aMap[axis][1]; 
    var sinAng = Math.sin(angRad), cosAng = Math.cos(angRad);
    var matB = matA.slice(0);
    for ( var i = 0; i < 16; ++ i ) matB[i] = matA[i];
    for ( var i = 0; i < 3; ++ i ) {
        matB[a0*4+i] = matA[a0*4+i] * cosAng + matA[a1*4+i] * sinAng;
        matB[a1*4+i] = matA[a0*4+i] * -sinAng + matA[a1*4+i] * cosAng;
    }
    return matB;
}

function Rotate(matA, angRad, axis) {
    var s = Math.sin(angRad), c = Math.cos(angRad);
    var x = axis[0], y = axis[1], z = axis[2]; 
    matB = [
        x*x*(1-c)+c,   x*y*(1-c)-z*s, x*z*(1-c)+y*s, 0,
        y*x*(1-c)+z*s, y*y*(1-c)+c,   y*z*(1-c)-x*s, 0,
        z*x*(1-c)-y*s, z*y*(1-c)+x*s, z*z*(1-c)+c,   0,
        0,             0,             0,             1 ];
    return Multiply(matA, matB);
}    

function Multiply(matA, matB) {
    matC = IdentM44();
    for (var i0=0; i0<4; ++i0 )
        for (var i1=0; i1<4; ++i1 )
            matC[i0*4+i1] = matB[i0*4+0] * matA[0*4+i1] + matB[i0*4+1] * matA[1*4+i1] + matB[i0*4+2] * matA[2*4+i1] + matB[i0*4+3] * matA[3*4+i1]  
    return matC;
}

function Cross( a, b ) { return [ a[1] * b[2] - a[2] * b[1], a[2] * b[0] - a[0] * b[2], a[0] * b[1] - a[1] * b[0], 0.0 ]; }
function Dot( a, b ) { return a[0]*b[0] + a[1]*b[1] + a[2]*b[2]; }
function Normalize( v ) {
    var len = Math.sqrt( v[0] * v[0] + v[1] * v[1] + v[2] * v[2] );
    return [ v[0] / len, v[1] / len, v[2] / len ];
}

Camera = function( pos, target, up, fov_y, vp, near, far ) {
this.Time = function() { return Date.now(); }
this.pos = pos;
this.target = target;
this.up = up;
this.fov_y = fov_y;
this.vp = vp;
this.near = near;
this.far = far;
this.orbit_mat = this.current_orbit_mat = this.model_mat = this.current_model_mat = IdentM44();
this.mouse_drag = this.auto_spin = false;
this.auto_rotate = true;
this.mouse_start = [0, 0];
this.mouse_drag_axis = [0, 0, 0];
this.mouse_drag_angle = 0;
this.mouse_drag_time = 0;
this.drag_start_T = this.rotate_start_T = this.Time();
this.Ortho = function() {
    var fn = this.far + this.near;
    var f_n = this.far - this.near;
    var w = this.vp[0];
    var h = this.vp[1];
    return [
        2/w, 0,   0,       0,
        0,   2/h, 0,       0,
        0,   0,   -2/f_n,  0,
        0,   0,   -fn/f_n, 1 ];
};  
this.Perspective = function() {
    var n = this.near;
    var f = this.far;
    var fn = f + n;
    var f_n = f - n;
    var r = this.vp[0] / this.vp[1];
    var t = 1 / Math.tan( Math.PI * this.fov_y / 360 );
    return [
        t/r, 0, 0,          0,
        0,   t, 0,          0,
        0,   0, -fn/f_n,   -1,
        0,   0, -2*f*n/f_n, 0 ];
}; 
this.LookAt = function() {
    var mz = Normalize( [ this.pos[0]-this.target[0], this.pos[1]-this.target[1], this.pos[2]-this.target[2] ] );
    var mx = Normalize( Cross( this.up, mz ) );
    var my = Normalize( Cross( mz, mx ) );
    var tx = Dot( mx, this.pos );
    var ty = Dot( my, this.pos );
    var tz = Dot( [-mz[0], -mz[1], -mz[2]], this.pos ); 
    return [mx[0], my[0], mz[0], 0, mx[1], my[1], mz[1], 0, mx[2], my[2], mz[2], 0, tx, ty, tz, 1]; 
};
this.Orbit = function() {
    return Multiply(this.LookAt(), this.OrbitMatrix());
}; 
this.OrbitMatrix = function() {
    return (this.mouse_drag || (this.auto_rotate && this.auto_spin)) ? Multiply(this.current_orbit_mat, this.orbit_mat) : this.orbit_mat;
};
this.AutoModelMatrix = function() {
    return this.auto_rotate ? Multiply(this.current_model_mat, this.model_mat) : this.model_mat;
};
this.Update = function(vp_size) {
    if (vp_size)
        this.vp = vp_size;
    var current_T = this.Time();
    this.current_model_mat = IdentM44()
    if (this.mouse_drag) {
        this.current_orbit_mat = Rotate(IdentM44(), this.mouse_drag_angle, this.mouse_drag_axis);
    } else if (this.auto_rotate) {
        if (this.auto_spin ) {
            if (this.mouse_drag_time > 0 ) {
                var angle = this.mouse_drag_angle * (current_T - this.rotate_start_T) / this.mouse_drag_time;
                this.current_orbit_mat = Rotate(IdentM44(), angle, this.mouse_drag_axis);
            }
        } else {
            var auto_angle_x = Fract( (current_T - this.rotate_start_T) / 13000.0 ) * 2.0 * Math.PI;
            var auto_angle_y = Fract( (current_T - this.rotate_start_T) / 17000.0 ) * 2.0 * Math.PI;
            this.current_model_mat = RotateAxis( this.current_model_mat, auto_angle_x, 0 );
            this.current_model_mat = RotateAxis( this.current_model_mat, auto_angle_y, 1 );
        }
    }
};
this.ChangeMotionMode = function(drag, spin, auto ) {
    var new_drag = drag;
    var new_auto = new_drag ? false : auto;
    var new_spin = new_auto ? spin : false;
    change = this.mouse_drag != new_drag || this.auto_rotate != new_auto || this.auto_spin != new_spin; 
    if (!change)
        return;
    if (new_drag && !this.mouse_drag) {
        this.drag_start_T = this.Time();
        this.mouse_drag_angle = 0.0;
        this.mouse_drag_time = 0;
    }
    if (new_auto && !this.auto_rotate)
        this.rotate_start_T = this.Time();
    this.mouse_drag = new_drag; 
    this.auto_rotate = new_auto;  
    this.auto_spin = new_spin;
    this.orbit_mat = Multiply(this.current_orbit_mat, this.orbit_mat);
    this.current_orbit_mat = IdentM44();
    this.model_mat = Multiply(this.current_model_mat, this.model_mat);
    this.current_model_mat = IdentM44();
};
this.OnMouseDown = function( event ) {
    var rect = gl.canvas.getBoundingClientRect();
    if ( event.clientX < rect.left || event.clientX > rect.right ) return;
    if ( event.clientY < rect.top || event.clientY > rect.bottom ) return;
    if (event.button == 0) { // left button
        this.mouse_start = [event.clientX, event.clientY]; 
        this.ChangeMotionMode( true, false, false );
    }
};
this.OnMouseUp = function( event ) {
    if (event.button == 0) { // left button
        this.ChangeMotionMode( false, true, true );
    } else if (event.button == 1) {// middle button
        this.ChangeMotionMode( false, false, !this.auto_rotate );
    }
};
this.OnMouseMove = function( event ) {
    var dx = (event.clientX-this.mouse_start[0]) / this.vp[0];
    var dy = (event.clientY-this.mouse_start[1]) / this.vp[1];
    var len = Math.sqrt(dx*dx + dy*dy);
    if (this.mouse_drag && len > 0) {
        this.mouse_drag_angle = Math.PI*len;
        this.mouse_drag_axis = [dy/len, 0, -dx/len];
        this.mouse_drag_time = this.Time() - this.drag_start_T;
    }
};

this.domElement = document;
var cam = this;
//this.domElement.addEventListener( 'contextmenu', function(e) { event.preventDefault(); }, false );
this.domElement.addEventListener( 'mousedown', function(e) { cam.OnMouseDown(e) }, false );
this.domElement.addEventListener( 'mouseup', function(e) { cam.OnMouseUp(e) }, false );
this.domElement.addEventListener( 'mousemove', function(e) { cam.OnMouseMove(e) }, false );
//this.domElement.addEventListener( 'mousewheel', hid_events.onMouseWheel, false );
//this.domElement.addEventListener( 'DOMMouseScroll', hid_events.onMouseWheel, false ); // firefox
}

var ShProg = {
Create: function (shaderList) {
    var shaderObjs = [];
    for (var i_sh = 0; i_sh < shaderList.length; ++i_sh) {
        var shderObj = this.Compile(shaderList[i_sh].source, shaderList[i_sh].stage);
        if (shderObj) shaderObjs.push(shderObj);
    }
    var prog = {}
    prog.progObj = this.Link(shaderObjs)
    if (prog.progObj) {
        prog.attrInx = {};
        var noOfAttributes = gl.getProgramParameter(prog.progObj, gl.ACTIVE_ATTRIBUTES);
        for (var i_n = 0; i_n < noOfAttributes; ++i_n) {
            var name = gl.getActiveAttrib(prog.progObj, i_n).name;
            prog.attrInx[name] = gl.getAttribLocation(prog.progObj, name);
        }
        prog.uniLoc = {};
        var noOfUniforms = gl.getProgramParameter(prog.progObj, gl.ACTIVE_UNIFORMS);
        for (var i_n = 0; i_n < noOfUniforms; ++i_n) {
            var name = gl.getActiveUniform(prog.progObj, i_n).name;
            prog.uniLoc[name] = gl.getUniformLocation(prog.progObj, name);
        }
    }
    return prog;
},
AttrI: function (prog, name) { return prog.attrInx[name]; },
UniformL: function (prog, name) { return prog.uniLoc[name]; },
Use: function (prog) { gl.useProgram(prog.progObj); },
SetI1: function (prog, name, val) { if (prog.uniLoc[name]) gl.uniform1i(prog.uniLoc[name], val); },
SetF1: function (prog, name, val) { if (prog.uniLoc[name]) gl.uniform1f(prog.uniLoc[name], val); },
SetF2: function (prog, name, arr) { if (prog.uniLoc[name]) gl.uniform2fv(prog.uniLoc[name], arr); },
SetF3: function (prog, name, arr) { if (prog.uniLoc[name]) gl.uniform3fv(prog.uniLoc[name], arr); },
SetF4: function (prog, name, arr) { if (prog.uniLoc[name]) gl.uniform4fv(prog.uniLoc[name], arr); },
SetM33: function (prog, name, mat) { if (prog.uniLoc[name]) gl.uniformMatrix3fv(prog.uniLoc[name], false, mat); },
SetM44: function (prog, name, mat) { if (prog.uniLoc[name]) gl.uniformMatrix4fv(prog.uniLoc[name], false, mat); },
Compile: function (source, shaderStage) {
    var shaderScript = document.getElementById(source);
    if (shaderScript)
        source = shaderScript.text;
    var shaderObj = gl.createShader(shaderStage);
    gl.shaderSource(shaderObj, source);
    gl.compileShader(shaderObj);
    var status = gl.getShaderParameter(shaderObj, gl.COMPILE_STATUS);
    if (!status) alert(gl.getShaderInfoLog(shaderObj));
    return status ? shaderObj : null;
},
Link: function (shaderObjs) {
    var prog = gl.createProgram();
    for (var i_sh = 0; i_sh < shaderObjs.length; ++i_sh)
        gl.attachShader(prog, shaderObjs[i_sh]);
    gl.linkProgram(prog);
    status = gl.getProgramParameter(prog, gl.LINK_STATUS);
    if ( !status ) alert(gl.getProgramInfoLog(prog));
    return status ? prog : null;
} };

function generateSSAOTextures( kernelSize, noiseSize, kernelTexUnit, noiseTexUnit ) {
    var ssaoObject = {}
    
    ssaoObject.kernel = new Uint8Array( kernelSize * 4 );
    for ( var i_k = 0; i_k < kernelSize; ++ i_k ) {
      var x = Math.random() * 2.0 - 1.0;
      var y = Math.random() * 2.0 - 1.0;
      var z = Math.random() * 2.0 - 1.0;
      var len = Math.sqrt( x * x + y * y + z * z );
      var w = i_k / kernelSize;
      w = 0.1 + 0.9 * w * w;
      ssaoObject.kernel[i_k*4] = ( x / len + 1.0 ) * 0.5 * 255.0;
      ssaoObject.kernel[i_k*4+1] = ( y / len + 1.0 ) * 0.5 * 255.0;
      ssaoObject.kernel[i_k*4+2] = ( z / len + 1.0 ) * 0.5 * 255.0;
      ssaoObject.kernel[i_k*4+3] = w * 255.0;
    }

    ssaoObject.noise = new Uint8Array( noiseSize * noiseSize * 4 );
    for ( var i_n = 0; i_n < noiseSize * noiseSize; ++ i_n ) {
      var x = Math.random() * 2.0 - 1.0;
      var y = Math.random() * 2.0 - 1.0;
      var z = Math.random() * 2.0 - 1.0;
      var len = Math.sqrt( x * x + y * y + z * z );
      ssaoObject.noise[i_n*4] = ( x / len + 1.0 ) * 0.5 * 255.0;
      ssaoObject.noise[i_n*4+1] = ( y / len + 1.0 ) * 0.5 * 255.0;
      ssaoObject.noise[i_n*4+2] = ( z / len + 1.0 ) * 0.5 * 255.0;
      ssaoObject.noise[i_n*4+3] = 255.0;
    }

    gl.activeTexture( gl.TEXTURE0+kernelTexUnit );
    ssaoObject.kernelTexUnit = kernelTexUnit;
    ssaoObject.kernelTexture = gl.createTexture();
    gl.bindTexture( gl.TEXTURE_2D, ssaoObject.kernelTexture );
    gl.texImage2D( gl.TEXTURE_2D, 0, gl.RGBA, kernelSize, 1, 0, gl.RGBA, gl.UNSIGNED_BYTE, ssaoObject.kernel );
    gl.texParameteri( gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST );
    gl.texParameteri( gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST );
    gl.texParameteri( gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.REPEAT );
  	gl.texParameteri( gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.REPEAT );
    
    gl.activeTexture( gl.TEXTURE0+noiseTexUnit );
    ssaoObject.noiseTexUnit = noiseTexUnit;
    ssaoObject.noiseTexture = gl.createTexture();
    gl.bindTexture( gl.TEXTURE_2D, ssaoObject.noiseTexture );
    gl.texImage2D( gl.TEXTURE_2D, 0, gl.RGBA, noiseSize, noiseSize, 0, gl.RGBA, gl.UNSIGNED_BYTE, ssaoObject.noise );
    gl.texParameteri( gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST );
    gl.texParameteri( gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST );
    gl.texParameteri( gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.REPEAT );
  	gl.texParameteri( gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.REPEAT );

    gl.activeTexture( gl.TEXTURE0 );
    return ssaoObject;
  };

var VertexBuffer = {
Create: function(attribs, indices, type) {
    var buffer = { buf: [], attr: [], inx: gl.createBuffer(), inxLen: indices.length, primitive_type: type ? type : gl.TRIANGLES };
    for (var i=0; i<attribs.length; ++i) {
        buffer.buf.push(gl.createBuffer());
        buffer.attr.push({ size : attribs[i].attrSize, loc : attribs[i].attrLoc, no_of: attribs[i].data.length/attribs[i].attrSize });
        gl.bindBuffer(gl.ARRAY_BUFFER, buffer.buf[i]);
        gl.bufferData(gl.ARRAY_BUFFER, new Float32Array( attribs[i].data ), gl.STATIC_DRAW);
    }
    gl.bindBuffer(gl.ARRAY_BUFFER, null);
    if ( buffer.inxLen > 0 ) {
        gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, buffer.inx);
        gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, new Uint16Array( indices ), gl.STATIC_DRAW);
        gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, null);
    }
    return buffer;
},
Draw: function(bufObj) {
    for (var i=0; i<bufObj.buf.length; ++i) {
        gl.bindBuffer(gl.ARRAY_BUFFER, bufObj.buf[i]);
        gl.vertexAttribPointer(bufObj.attr[i].loc, bufObj.attr[i].size, gl.FLOAT, false, 0, 0);
        gl.enableVertexAttribArray( bufObj.attr[i].loc);
    }
    if ( bufObj.inxLen > 0 ) {
        gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, bufObj.inx);
        gl.drawElements(bufObj.primitive_type, bufObj.inxLen, gl.UNSIGNED_SHORT, 0);
        gl.bindBuffer( gl.ELEMENT_ARRAY_BUFFER, null );
    }
    else
        gl.drawArrays(bufObj.primitive_type, 0, bufObj.attr[0].no_of );
    for (var i=0; i<bufObj.buf.length; ++i)
        gl.disableVertexAttribArray(bufObj.attr[i].loc);
    gl.bindBuffer( gl.ARRAY_BUFFER, null );
} };

var FrameBuffer = {};
FrameBuffer.Create = function( vp, texturePlan ) {
    var texPlan = texturePlan ? new Uint8Array( texturePlan ) : null;
    var fb = gl.createFramebuffer();
    var fbsize = Math.max(vp[0], vp[1]);
    fbsize = 1 << 31 - Math.clz32(fbsize); // nearest power of 2
    fb.width = fbsize;
    fb.height = fbsize;
    gl.bindFramebuffer( gl.FRAMEBUFFER, fb );
    fb.color0_texture = gl.createTexture();
    gl.bindTexture( gl.TEXTURE_2D, fb.color0_texture );
    gl.texImage2D( gl.TEXTURE_2D, 0, gl.RGBA, fb.width, fb.height, 0, gl.RGBA, gl.UNSIGNED_BYTE, texPlan );
    gl.texParameteri( gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST );
    gl.texParameteri( gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST );
    fb.renderbuffer = gl.createRenderbuffer();
    gl.bindRenderbuffer( gl.RENDERBUFFER, fb.renderbuffer );
    gl.renderbufferStorage( gl.RENDERBUFFER, gl.DEPTH_COMPONENT16, fb.width, fb.height );
    gl.framebufferTexture2D( gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, fb.color0_texture, 0 );
    gl.framebufferRenderbuffer( gl.FRAMEBUFFER, gl.DEPTH_ATTACHMENT, gl.RENDERBUFFER, fb.renderbuffer );
    gl.bindTexture( gl.TEXTURE_2D, null );
    gl.bindRenderbuffer( gl.RENDERBUFFER, null );
    gl.bindFramebuffer( gl.FRAMEBUFFER, null );

    fb.Bind = function( clear ) {
        gl.bindFramebuffer( gl.FRAMEBUFFER, this );
        if ( clear ) {
            gl.viewport( 0, 0, this.width, this.height );
            gl.clearColor( 0.0, 0.0, 0.0, 1.0 );
            gl.clear( gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT );
        }
    };

    fb.Release = function( clear ) {
        gl.bindFramebuffer( gl.FRAMEBUFFER, null );
        if ( clear ) {
            gl.clearColor( 0.0, 0.0, 0.0, 1.0 );
            gl.clear( gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT );
        }
    };

    fb.BindTexture = function( textureUnit ) {
        gl.activeTexture( gl.TEXTURE0 + textureUnit );
        gl.bindTexture( gl.TEXTURE_2D, this.color0_texture );
    };

    return fb;
}  

function Fract( val ) { 
    return val - Math.trunc( val );
}
function CalcAng( deltaMS, intervall ) {
    return Fract( deltaMS / (1000*intervall) ) * 2.0 * Math.PI;
}
function CalcMove( deltaMS, intervall, range ) {
    var pos = self.Fract( deltaMS / (1000*intervall) ) * 2.0
    var pos = pos < 1.0 ? pos : (2.0-pos)
    return range[0] + (range[1] - range[0]) * pos;
}    
function EllipticalPosition( a, b, angRag ) {
    var a_b = a * a - b * b
    var ea = (a_b <= 0) ? 0 : Math.sqrt( a_b );
    var eb = (a_b >= 0) ? 0 : Math.sqrt( -a_b );
    return [ a * Math.sin( angRag ) - ea, b * Math.cos( angRag ) - eb, 0 ];
}

initScene();

})(); 

</script>
